Intenret Marketing is a huge subject that's practiced and discussed by people from all walks of life. It's recently been adopted as an industry in itself. It's seperate to web development, and offline marketing, although it's closely linked to web development because of things like "on page seo" it's still a seperate entity.

There are hundreds, if not thousands of areas to Internet Marketing. Countless websites and forums exist to discuss the subject, which is why I think it would be great if Stack Exchange could host a Q&A website on the subject.